Varieties of temperature measuring devices have generally been available in various different industrial fields to detect temperatures of objects to be measured such as fluids or solids.
In a medical field for example, various types of temperature controls are carried out utilizing hypothermic methods and normal temperature circulation methods, etc., in extracorporeal circulation with use of an artificial heart-lung machine etc., and in that case blood temperature in the extracorporeal circulation has been measured by temperature measuring devices of all sorts.
FIGS. 1 and 2 illustrate such prior temperature measuring devices.
As illustrated in FIG. 1, a prior temperature measuring device 2 mainly includes a synthetic resin cylindrical member 4, a closed-end tube 6 attached fixedly to the cylindrical member 4 in a liquid tight manner at its end on its opening side, and a temperature sensor 8 detachably mounted interiorly of the closed-end tube 6. The cylindrical member 4 is bonded to a housing 10 such as a casing of an artificial heart-lung machine, and the closed-end tube 6 allows its closed-end part to enter the housing 10, i.e., the blood passageway 12, to a predetermined depth.
In such configuration, the closed-end tube 6 protruding into the blood passageway 12 defined in the housing 10 informs the temperature sensor 8 of the temperature of blood flowing in the blood passageway 12, for measurement of the same through the temperature sensor 8.
In the prior temperature measuring device, however, the closed-end tube 6, which protrudes deeply into the blood passageway 12, perturbs the blood flow in the vicinity thereof to produce hemagglutination there around and damage blood cells.
Further, as illustrated in FIG. 2, a temperature measuring device of another type includes a body 18, to both ends of which circulation lines 16, 16 are connectable, a blood flow passageway 22 defined interiorly of the body 18, and a temperature sensor 20 facing the blood flow passageway 22.
Thus, the prior temperature measuring device 14 of the second example also has a drawback in the same manner as in the first example shown in FIG. 1 in that the temperature sensor 20 tends to perturb the blood flow in the blood flow passageway 22 and damage blood cells flowing in the passageway 22.
To solve the above drawback, it might be considered that the depth of the insertion of the temperature sensor 20 into the blood flow passageway 22 should be made as small as possible. This however produces a severe influence of ambient temperature on the temperature sensor 20, impeding an accurate measurement of the blood temperature by the temperature sensor 20.
Additionally, those prior temperature measuring devices 2, 14 have no insulating means, thus causing an extraneous voltage to be applied on blood flowing through the blood flow passageways 12, 22.